Experiments and analyses of supercritical CO2 flow instability with study of wall heat-storage and dimensionless parameters

Abstract

This paper reports both experiments and analyses of supercritical CO2 in two heated vertical parallel channels. The intent of the present experiments was to search for static instability in an up-flow system. However, no static instability was found using CO2. A total of 18 experiments at different flow conditions were performed with supercritical CO2 flowing upwards. Eleven were already published by Saini et al. [1] and 7 new cases are presented here. For all cases, oscillatory flow instability was observed. The 18 flow instability cases were numerically modeled to assess the performance of the in-house developed linear, frequency-domain program without and with wall-heat storage. The predicted numerical results agreed well with the experimental results in all cases. The study showed that including wall-heat storage, for this two channel systems, has a very minor effect on the flow instability boundary. Additionally, the accuracy of the supercritical flow dimensionless parameters proposed by Ambrosini and Sharabi [2], to convert experimental CO2 instability data to water within the same loop, was examined. The dimensionless parameters performed very well. There was also very good agreement between experiment and code on the oscillation period.